1. Field of the Invention
The technical scope of the invention is that of processes and devices to guide and/or steer a projectile towards a target.
2. Description of the Related Art
Known projectiles are guided towards their target by a guiding device which establishes acceleration correction commands to be applied to the projectile to direct it to the target.
These correction commands are then used by a steering device which establishes the commands to be applied to the steering organs so as to ensure the required correction.
Thus, autonomous projectiles are known that have a satellite positioning system (more commonly known by the acronym “Global Positioning System” or GPS) which enables them to be located on a trajectory. Before being fired, the projectile is programmed with the coordinates of the target. It thus determines its in-flight position itself and establishes, using data supplied by an inertial measurement unit on-board and by means of appropriate algorithms, the commands to be transmitted to the fins.
This inertial measurement unit comprises accelerometers and gyrometers (or gyroscopes) which supply (in a projectile-linked reference marker) the components of the instantaneous rotation vector and non-gravitational acceleration to which the projectile is subjected. This inertial measurement unit is implemented both to ensure the steering of the projectile and contributes to its guidance by combining the data from this unit with that supplied by the GPS.
It is also known to produce projectiles incorporating a target detector enabling it to be located in space.
In this case, the guiding and steering set points are established from the direction of location of the target with respect to the projectile (line of sight) and also from the data related to the spin of this line of sight with respect to a fixed reference marker (first approximation terrestrial reference marker) expressed in a projectile-linked reference marker.
The movements of the line of sight are measured with respect to a projectile-linked reference marker, whereas in order to guide the projectile the movements of the line of sight with respect to a fixed reference marker need to be known.
Data regarding the behavior of the projectile with respect to a fixed reference marker is obtained by using an inertial measurement unit. It is thus possible for the movements of the line of sight to be determined with respect to a fixed reference marker. Once again, this inertial measurement unit is implemented both to ensure the steering of the projectile and contributes to its guidance.
It is thus possible for the correction acceleration for the projectile to be defined in a projectile-linked reference marker for it to reach the target.
If these solutions are well adapted to missile-type projectiles, they cannot be used for cannon-fired projectiles because of the lack of robustness of the gyrometers and the excessive cost of these measurement components.